Chemical zoning of garnet is often used to deduce P–T paths of rocks by inverse calculation. To validate the derived P–T paths, it is desired to establish a method to predict the chemical compositions of garnet theoretically. This study proposes a new forward calculation of the formation of Mg–Fe–Mn garnet from chlorite, which solves the non-linear simultaneous equations using nested iterative calculations. Growth of garnet consuming chlorite and quartz was modelled in a MnO–FeO–MgO–Al₂O₃–SiO₂–H₂O system, using the most recent thermodynamic data for the minerals. The prograde P–T history of the Sambagawa metamorphic belt, SW Japan, was modelled. To reproduce growth zoning, crystallized garnet was removed step by step from the system; perfect diffusion was assumed for chlorite. The proposed model derived the evolution of molar amounts and chemical compositions of Mg–Fe–Mn chlorite and garnet. It successfully reproduced the shape of the observed chemical profile of garnet, although the temperature condition was higher than general observations. The Mn content of the garnet core was generally high, and Mg/Fe ratio always started rising rapidly after Mn was depleted. Thermodynamic properties of minerals, initial chlorite composition, P–T path, H₂O partial pressure, and Ca content in garnet were varied to test the behaviour of the system. The properties of Mn phases influenced only the chemical composition of the garnet core. The temperature range in which garnet grew depended on the H₂O partial pressure or the Ca content in garnet.

Granite powder (stone powder), a waste product generated from stone quarries, is increasingly being reused in cement-treated clays. The particle size of stone powders affects the cement-clay reaction by either increasing or reducing the unconfined compressive strength (UCS). This study investigated this phenomenon by separating stone powder from the same batch at the quarry into five particle sizes (A, B, C, D and E: 106–75 µm, 40–75 µm, 20–40 µm, <20 µm and 106– E > C > B > A, which translated into UCS variation in the same order. Stone powders D and E played two roles in UCS development, i.e., nucleation of cementitious products and reaction with Ca(OH)₂ to increase the UCS higher than the control sample. Linear regression equations determined the minimum concentration of amorphous silica for a UCS increment as 9.4 mg/g.

The beginning of the recrystallization of minerals within a subducting oceanic plate provides a valuable record of dehydration within the subduction zone. Pelitic schists of the Nagatoro area, Kanto Mountains, Japan, record the initial stages of garnet growth. Consequently, these rocks were studied to analyze garnet nucleation and growth during metamorphism of the Sanbagawa metamorphic belt, one of the world’s most comprehensively studied subduction complexes. The garnet grains are small, euhedral, and occur only within micaceous lamellae that define the schistosity. Crystal size distribution analyses revealed most of the garnet grains follow the log-normal size distribution, indicating that they formed in the same event. A few exceptionally large garnet grains exist that do not seem to follow the log-normal distribution. The latter garnet grains contain a rounded fragmental area with a different chemical composition inside the core. It is possible that detrital fragments of garnet contribute to the irregular crystal size distribution of garnet in the studied area. Many of the smaller (log-normal) garnet grains have relatively large, homogeneous Mn-rich cores. The lack of chemical zoning within the garnet cores suggests that they grew under constant pressure and temperature in response to overstepping of the garnet-in reaction. The chemical composition changes very sharply at the boundary between the core and the surrounding mantle. The size of the Mn-rich core is different from sample to sample, suggesting that the nucleation was controlled by the local chemical condition of each sample.